Roslon, I. | Search bioRxiv

bioRxiv2023

Microwell-enhanced optical detection of single bacteria

Bacteria that are resistant to antibiotics present an increasing burden on healthcare. To address this emerging crisis, novel rapid Antibiotic Susceptibility Testing (AST) methods are eagerly needed. Here, we present an optical AST technique that can determine the bacterial viability within one hour down to a resolution of single bacteria. The method is based on measuring intensity fluctuations of a reflected laser focused on a bacterium in reflective microwells. Using numerical simulations, we show that both refraction and absorption of light by the bacterium contribute to the observed signal. By administering antibiotics that kill the bacteria, we show that the variance of the detected fluctuations vanishes within one hour, indicating the potential of this technique for rapid sensing of bacterial antibiotic susceptibility. We envisage the use of this method for massively parallelizable AST tests and fast detection of drug resistant pathogens.

bioengineering↗

bioRxiv2021

Probing nanomotion of single bacteria with graphene drums

Motion is a key characteristic of every form of life1. Even at the microscale, it has been reported that colonies of bacteria can generate nanomotion on mechanical cantilevers2, but the origin of these nanoscale vibrations has remained unresolved3,4. Here, we present a novel technique using drums made of ultrathin bilayer graphene, where the nanomotion of single bacteria can be measured in its aqueous growth environment. A single E. coli cell is found to generate random oscillations with amplitudes of up to 60 nm, exerting forces of up to 6 nN to its environment. Using mutant strains, we are able to pinpoint the bacterial flagella as the main source of nanomotion. By real-time tracing of changes in nanomotion upon administering antibiotics, we demonstrate that graphene drums can perform antibiotic susceptibility testing with single-cell sensitivity. These findings deepen our understanding of processes underlying cellular dynamics, and pave the way towards high throughput and parallelized rapid screening of the effectiveness of antibiotics in bacterial infections with graphene devices.

biophysics↗